Automated distributed antenna system self-configuration

ABSTRACT

Certain features relate to systems and methods for planning and optimizing a distributed antenna system (“DAS”) based on measurements taken from the radio environment surrounding the DAS. An operation and management system can determine a mapping of external cells based on measurements of downlink signals taken by a measurement subsystem. The operation and management system can determine a mapping of internal cells as well as a neighboring cell relation table. The DAS element management system or network operator can configure the DAS based on the mapping of external cells, mapping of internal cells, and the cell relation table. Additionally, based on neighboring cell signal power measurements taken by user devices, the a common interface between the DAS and the radio access network can determine a radio environment map estimating positions of the user devices connected to the DAS.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage application of PCT ApplicationSerial No. PCT/US2015/036772, filed Jun. 19, 2015, and titled “AUTOMATEDDISTRIBUTED ANTENNA SYSTEM SELF-CONFIGURATION,” which claims the benefitof U.S. Provisional Application Ser. No. 62/014,939, filed Jun. 20, 2014and titled “Automated Distributed Antenna System Self-Configuration,”the contents of all of which are hereby incorporated herein byreference.

TECHNICAL FIELD

The disclosure relates generally to telecommunications and, moreparticularly (although not necessarily exclusively), to automaticself-configuration of a telecommunications network by determining theradio environment of the telecommunications network.

BACKGROUND

A distributed antenna system (“DAS”) can include one or more head-endunits and multiple remote units coupled to each head-end unit. A DAS canbe used to extend wireless coverage in an area. Head-end units can beconnected to base stations. A head-end unit can receive downlink signalsfrom the base station and distribute downlink signals in analog ordigital format to one or more remote units. The remote units cantransmit the downlink signals to user equipment devices within coverageareas serviced by the remote units. In the uplink direction, signalsfrom user equipment devices may be received by the remote units. Theremote units can transmit the uplink signals received from userequipment devices to a head-end unit. The head-end unit can transmituplink signals to the serving base stations.

In a simulcast mode, each downlink cell signal associated with a basestation can be distributed across multiple DAS remote units such thatmultiple DAS remote units radiate the same downlink cell signal. It canbe difficult in the simulcast mode to determine neighboringrelationships down to each remote unit between cells inside the DAS andcells outside the DAS. An internal cell can refer to a cell associatedwith a base station connected to the DAS. An external cell can refer toany other cell associated with base stations not connected to the DAS,which can include cells belonging to a cellular communications network.In a scenario in which a DAS is located, for example, in a building, theradio footprint of external cells may overlap with the radio footprintof the internal cells associated with the remote units inside thebuilding. Using the same cell ID for both an internal cell and anexternal cell can create a cell ID conflict which can degrade theoverall network performance.

SUMMARY

In one aspect, a method is provided. The method can include determininga mapping of external cells from measurements of external downlinksignals received by a remote unit of a distributed antenna system. Theremote unit provides wireless communication within a coverage zone. Themethod can also include determining a mapping of internal cells frommeasurements of internal downlink signals provided by base stationscommunicatively coupled to a head-end unit of the distributed antennasystem. The method can further include determining relation informationof neighboring cells. Neighboring cells include radio footprints thatoverlap with the coverage zone of the remote unit. The method can alsoinclude configuring the distributed antenna system and the base stationsbased on the mapping of external cells, the mapping of internal cells,and the relation information of neighboring cells.

In another aspect, a head-end unit is provided. The head-end unit caninclude a measurement subsystem configured to measure external downlinksignals detected by a remote unit of a distributed antenna system andmeasure internal downlink signals provided from an internal base stationcommunicatively coupled to the distributed antenna system. The head-endunit can also include an operation and management system configured todetermine, from the external downlink signals, a mapping of externalcells detected by the remote unit. The operation and management systemis also configured to determine, from the internal downlink signals, amapping of internal cells, and determine relation information ofneighboring cells. Neighboring cells include radio footprints thatoverlap with a coverage zone of the remote unit. The head-end unit canbe configured to provide wireless communication from the internal basestation to the remote unit and additional remote units of thedistributed antenna system.

In another aspect, a distributed antenna system is provided. Thedistributed antenna system can include one or more remote unitsconfigured to provide wireless communication to user devices within acoverage zone. The distributed antenna system can also include ahead-end unit communicatively coupled to the one or more remote units.The head-end unit includes an operation and management system configuredto determine a mapping of external cells, a mapping of internal cells,and relation information of neighboring cells for each remote unit inthe distributed antenna system. The operation and management system alsoprovides the mapping of external cells, the mapping of internal cells,and the relation information of neighboring cells to an elementmanagement system communicatively coupled to the head-end unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of management architecturefor a radio access network (“RAN”) and distributed antenna system(“DAS”) with a measurement subsystem included in a head-end unit of theDAS according to one aspect of the present disclosure.

FIG. 2 is a schematic diagram showing an example of a radio coverage mapof remote units communicating with internal cells according to oneaspect of the present disclosure.

FIG. 3 is a flowchart showing an example of a process for mapping aradio coverage map and configuring a distributed antenna systemaccording to one aspect of the present disclosure.

FIG. 4 is a table mapping examples of internal cell pilot power levelsfor each remote unit in a distributed antenna system according to oneaspect of the present disclosure.

FIG. 5 is a table mapping examples of external cell pilot power levelsfor each remote unit in a distributed antenna system according to oneaspect of the present disclosure.

FIG. 6 is a table indicating examples of neighboring cells for eachremote unit in a distributed antenna system according to one aspect ofthe present disclosure.

FIG. 7 is a block diagram showing an example of management architecturefor a RAN and DAS with measurement subsystems included in the remoteunits of the DAS according to one aspect of the present disclosure.

FIG. 8 is a schematic diagram showing an example of a radio coverage mapof remote units and user devices in a distributed antenna system.

FIG. 9 is a block diagram showing an example of management architecturefor a RAN and a DAS with a common interface between a DAS elementmanagement system (“EMS”) and RAN EMS according to one aspect of thepresent disclosure.

FIG. 10 is a block diagram showing an example of management architecturefor a RAN and a DAS with a common interface between internal basestations and the DAS head-end unit according to one aspect of thepresent disclosure.

FIG. 11 is a flowchart showing an example of a process for determining aradio coverage map of user devices in a DAS according to one aspect ofthe present disclosure according to one aspect of the presentdisclosure.

FIG. 12 is a table indicating examples of power levels measured by userdevices in a DAS according to one aspect of the present disclosure.

FIG. 13 is a table indicating examples of power levels measured byremote units in a DAS according to one aspect of the present disclosure.

FIG. 14 is a table indicating examples of comparisons of power levelsmeasured by remote units in a DAS and by user devices communicating witha DAS according to one aspect of the present disclosure.

DETAILED DESCRIPTION

Certain aspects and features are directed to automated methods andsystems for planning and optimizing a telecommunications system, such asa distributed antenna system (“DAS”), based on measurements derived fromthe radio environment surrounding the DAS. For example, a DAS can bepart of a larger radio access network (“RAN”) where some of the remoteunits and user devices that are part of the DAS fall within overlappingradio coverage zones of cells outside of the DAS. Remote units and userdevices within the DAS can detect incoming downlink signals from bothinternal base stations that are connected to the DAS and external basestations that are part of other telecommunications networks and haveoverlapping radio coverage zones.

The DAS may not have control over the configuration and cell identifier(“ID”) selection of the cells outside of the DAS. Certain aspects of thepresent disclosure relate to automatically detecting the radioenvironment around the DAS and identifying areas of overlapping radiofootprints. This information can be provided to a network managementsystem of the RAN for planning and automatically adjusting the layout ofcells and cell IDs within the DAS. For example, when assigning cell IDs,the network management system can avoid assigning the detected cell IDsof cells outside the DAS as the cell IDs internal to the DAS.Automatically configuring the DAS based on the detected radioenvironment map can mitigate the likelihood of signaling errorsresulting from of conflicting cell ID selections.

For example, a measurement subsystem and an operation and managementsystem can be used to identify cells that are internal to the DAS andcells that are external to the DAS and determine areas of overlappingradio coverage. The measurement subsystem and operation and managementsystem can also determine, for each remote unit in the DAS, anyneighboring cells that have overlapping radio footprints with thecoverage zone of the remote unit. The internal/external cell IDinformation and the neighboring cell information can be used toautomatically plan and adjust the layout of cell IDs within the DAS. Thelayout of the DAS cells can be configured, for example, such that theinternal cell IDs do not conflict with external cell IDs assigned by theradio access network.

For example, in one aspect for automated DAS self-configuration, thehead-end unit can instruct all remote units of the DAS to operate in adownlink monitoring mode, where remote units detect incoming signals ondownlink frequency bands in which the DAS operates. A DAS measurementsystem, which can be located in the head-end unit, can detect parametersfrom the downlink signals from each remote unit. The downlink signalparameters can include, for example, the pilot power (e.g., LTE RSRPpilot tone power), the physical cell ID of the cell associated with thetransmission, the global cell ID, the mobile country code, mobilenetwork code, carrier technology (e.g., LTE, UMTS, etc.) bandwidth ofthe signal, and the frequency of the signal. An operation and managementsystem, which can also be located in the head-end unit, can use thedetected parameters to generate an external cell table indicating whichremote units detected downlink signals from external cells.

The operation and management system in the DAS can also generate aninternal cell ID table by measuring the downlink input signal from eachbase station connected to the DAS. The DAS measurement subsystem candetect the internal cell IDs and signal pilot power for the internalcells. This information can be used to generate an internal cell tablethat indicates which remote units are included in each cell. Theinternal cell table and the external cell table can be combined tocreate a neighboring cell relationship table, which can define therelationships between cells and be used to automatically configure theDAS by optimizing the internal cell ID selection in order to avoid cellID collision.

In some aspects, the DAS measurement subsystem can detect and measuresignal interference that may be caused by conflicting frequency bandsused by both the internal cell and a neighboring external cell. The DAScan use the measured signal interference to determine which carrierfrequencies conflict. In response, the operation and management systemcan adjust the carrier frequencies used in the DAS to avoid conflictswith external carrier frequencies.

In another aspect, additional measurements can be taken at each userdevice connected to the DAS. User devices can be instructed by the basestation to perform measurements of downlink signal parameters similar tothe measurements performed by the DAS measurement system. The basestation can provide the measurements performed by the user devices tothe RAN element management system and network management system. The RANnetwork management system, in turn, can collect and compare themeasurements of downlink signal parameters from the user devices as wellas the measurements from the DAS measurement system. The RAN networkmanagement system can use the comparison of measured downlink signalparameters to estimate relative positions of each user device.

In another aspect, the measurements taken by each user device can becompared with the internal cell and external cell information in orderto estimate the relative position of the user devices in relation toeach remote unit in the DAS. This can help determine traffic hotspots inthe DAS, allowing a system operator to increase DAS coverage whereneeded.

These illustrative aspects and examples are given to introduce thereader to the general subject matter discussed here and are not intendedto limit the scope of the disclosed concepts. The following sectionsdescribe various additional features and examples with reference to thedrawings in which like numerals indicate like elements, and directionaldescriptions may be used to describe the illustrative aspects but, likethe illustrative aspects, should not be used to limit the presentdisclosure.

FIG. 1 is a block diagram of an example of a management system for a RANand a DAS network suitable for implementing the subject matter describedherein. The management system can include a RAN element managementsystem 100, a DAS element management system 102, and an operator networkmanagement system 104. The management system shown in FIG. 1 can beconnected to operators serving various network formats (e.g., GSM, CDMA,UMTS, LTE). While a single operator network management system 104 isshown in FIG. 1 as an example, network management systems of multiplenetwork operators or the element management system of any RAN technologycan be included in the management system of FIG. 1 without departingfrom the scope of the subject matter described herein.

The operator network management system 104 can communicate with the DASelement management system 102 and the RAN element management system 100via a north-bound interface. A north-bound interface is an interfacethat allows a component of a telecommunications system to communicatewith a higher-level component in the network architecture. The DASelement management system 102 can be coupled to a DAS that includes ahead-end unit 116 coupled to one or more remote units 126 a-c. The RANelement management system 100 can be coupled to one or more basestations present in the RAN, such as internal base stations 106 a-b andexternal base station 112. The RAN element management system 100 cancommunicate with the internal base stations 106 a-b and the externalbase station 112 via a south-bound interface. Internal base stations 106a-b can provide wireless communication to components of the DAS, such asthe DAS remote units 126 a-c. The external base station 112 can providecommunication to any device or networking system not connected to theDAS. Accordingly, network cells associated with one of the internal basestations 106 a-b coupled to the DAS platform can be referred as internalcells, whereas all other cells coupled to external base stations, suchas external base station 112, can be referred to as external cells.

The internal base stations 106 a-b can provide wireless communication toremote units 126 a-c via the head-end unit 116. Any suitablecommunication link can be used for communication between internal basestations 106 a-b and head-end unit 116. Examples of a suitablecommunication link include a direct connection or a wireless connection.A direct connection can include, for example, a connection via a copper,optical fiber, or other suitable communication medium. In some aspects,the head-end unit 116 can include an external repeater or internal RFtransceiver to communicate with the internal base stations 106 a-b. Insome aspects, internal base stations 106 a-b can be communicativelycoupled to the head-end unit 116 with via a digital baseband interfaceinstead of a radio frequency interface. An example of a digital basebandinterface is an interface that follows the common public radio interface(CPRI) standard. When communicatively coupled with a digital basebandinterface, the head-end unit 116 can communicate with the internal basestations 106 a-b by communicating I/Q samples of radiated radiofrequency signals.

Downlink signals from the internal base stations 106 a-b are provided tothe head-end unit 116, which can provide the downlink wirelesscommunication to one or more of the intended remote units 126 a-c.Uplink signals sent from the remote units 126 a-c are provided to thehead-end unit 116, which can provide the uplink communication signals tothe appropriate base station 106 a-b.

The DAS element management system 102 and RAN element management system100 can manage various telecommunications network elements for the RANand DAS, respectively. For example, the DAS head-end unit 116 canprovide certain parameters, such as measured cell ID values ofneighboring cells and pilot power levels of neighboring cells to the DASelement management system 102 and the operator network management system104. The DAS element management system 102 and the operator networkmanagement system 104 can use the received parameters to determine theoptimal cell ID selection values for the DAS. The DAS element managementsystem 102 can configure aspects of the DAS by sending commands to anoperation and management/self-optimizing network unit 120 (OAM-SON unit)included in the head-end unit 116. Each internal base station 106 a-band the external base station 112 can include OAM-SON units 108 a-b and114, respectively, for communicating with the RAN element managementsystem 100. In other aspects, the OAM-SON units 108 a-b and 114 can befully decoupled from the internal base stations 106 a-b and externalbase station 112. In some aspects, system configuration and controlmessages can be exchanged between the OAM-SON units 108 a-b of internalbase stations 106 a-b and the OAM-SON unit 120 of the head-end unit 116.

The DAS head-end unit 116 can include a measurement subsystem 118 thatincludes signal-processing circuitry associated with receiving,demodulating, and decoding downlink cell signals from internal basestations 106 a-b coupled to the DAS and external base station 112. Themeasurement subsystem 118 can detect and decode downlink signals invarious network formats (e.g., GSM, CDMA, UMTS, LTE). Downlink signalsfrom internal base stations 106 a-b can be provided to the measurementsubsystem 118 via the digital wired or RF cable interfaces betweeninternal base stations 106 a-b and head-end unit 116. If remote units126 a-c are within the cell range of external base station 112, thenremote units can detect over-the-air downlink signals from external basestation 112 and provide the detected downlink signals to the measurementsubsystem 118.

The signal strength of downlink signals from the external base station112 can vary based on interference and noise from various other sources.To detect weak downlink signals from the external base station 112, thesensitivity of the measurement subsystem 118 can be increased bystopping downlink transmissions from the remote units 126 a-c andselectively muting the detection of downlink signals from remote unitsother than a target remote unit. The target remote unit can be rotateduntil downlink signals from all remote units 126 a-c are measured. Forexample, the measurement subsystem 118 can mute remote units 126 b-c andmeasure downlink signals detected from target remote unit 126 a. Themeasurement subsystem 118 can mute remote units 126 a, 126 c and measuredownlink signals detected from target remote unit 126 b. Finally, themeasurement subsystem 118 can mute remote units 126 a-b and measuredownlink signals detected from target remote unit 126 c. Muting can beperformed by the switch 124. Using the switch 124 or similar device toselectively mute signals from remote units other than a target unit canavoid adding together interference associated from multiple signals,thereby increasing the sensitivity of the measurement subsystem 118.

While certain aspects and features with respect to FIG. 1 depict themeasurement subsystem 118 as part of the head-end unit 116, in otheraspects, each remote unit can also include a measurement subsystem. Forexample, FIG. 7 is a block diagram illustrating a management system fora RAN and DAS with measurement subsystems in each remote unit accordingto one aspect. The management system can include an operator networkmanagement system 104, DAS element management system 102, and RANelement management system 100, all of which operate in a similar manneras described with respect to FIG. 1. The management system shown in FIG.7 can also include internal base stations 106 a-b connected to a DAS andexternal base station 112. The DAS shown in FIG. 7 can include ahead-end unit 702 with an OAM-SON unit 704, the head-end unit 702configured to provide communication from internal base stations 106 a-bto remote units 706 a-c. Each remote unit 706 a-c can include ameasurement subsystem 708 a-c. The measurement subsystem 708 a-c canfunction in a similar manner to measurement subsystem 118 discussed withrespect to FIG. 1. For example, to detect weak downlink signals fromexternal base station 112, sensitivity of the measurement subsystems 708a-c can be increased by stopping downlink transmissions from the remoteunits 706 a-c. Unlike the measurement subsystem 118 described withrespect to FIG. 1, however, each measurement subsystem 708 a-c canrespectively detect signals from external base station 112 withoutmuting the detection of downlink signals transmitted by the other remoteunits. Each remote unit 708 a-c can detect downlink signals in parallel.

Downlink signals broadcasted by internal base stations 106 a-b andexternal base station 112 can include system information parametersaccording to the relevant radio resource control protocol. Systeminformation parameters can include, but are not limited to, pilot tonepower (e.g., LTE RSRP), physical cell ID, and global cell ID. Themeasurement subsystem 118 can detect the system information parametersto determine which physical cell IDs correspond to internal cells andwhich correspond to external cells. The measurement subsystem 118 canalso determine neighboring cell relations for each remote unit 126 a-c(e.g., which internal cells and external cells are neighboring cells foreach remote unit) and provide this information to the DAS elementmanagement system 102. For example, internal cells corresponding to thecoverage zones of internal base stations 106 a-b can overlap withexternal cells corresponding to coverage zones of external base station112. The cell relations determined by the measurement subsystem 118 canbe used by the DAS element management system 102 and the operatornetwork management system 104 to optimally configure the cell IDs in thenetwork.

For example, FIG. 2 shows an example of a network involving sixteenremote units 202 a-p deployed within overlapping coverage zones frominternal cells 204 a-d and external cells 206 a-c. Four internal cells204 a-d are associated with signals from internal base stationsconnected to a DAS and uniformly allocated across the sixteen remoteunits 202 a-p. External cells 206 a-c are associated with signals fromother networks and external base stations not connected to the DAS. Theradio footprint of each DAS remote unit 202 a-p is shown for theinternal cells 204 a-d along with the radio footprints of the externalcells 206 a-c. The radio footprint of some cells overlap with the radiofootprint of other cells. The depicted signal fronts of the externalcells 206 a-c are related to a minimum power level threshold, which canbe detected by the DAS measurement subsystem. For example, remote units202 i, 202 m, located within the radio footprint of internal cell 204 c,can also detect downlink signals in external cell 206 a. Remote unit 202e, located within the radio footprint of internal cell 204 a, can alsodetect downlink signals in external cell 206 a. The remote unit 202 p,located within the coverage of internal cell 204 d, can also detectdownlink signals from any external base station in external cell 206 c.

Configuring a DAS Based on Measurements of External Downlink Signals andInternal Downlink Signals

A DAS with a measurement subsystem can identify external cell signalsoverlapping with internal cell signals as well as internal cell signalsoverlapping within each other. FIG. 3 is a flowchart depicting a processfor identifying the overlapping radio footprints of cells and optimizingthe associations of cell IDs in a DAS. In block 302, the OAM-SON unit120 and the measurement subsystem 118 can determine a mapping ofexternal cells from measurements of external downlink signals. Forexample, measurement subsystem 118 can perform measurements on externaldownlink signals detected by the remote units 126 a-c that are locatedwithin the radio footprint of any external base station To determine themeasurements of the external downlink signals, the OAM-SON unit 120 inhead-end unit 116 can set all of the remote units 126 a-c to aradio-monitoring mode. In the radio monitoring mode, remote units 126a-c can actively monitor over-the-air downlink signals provided by anyexternal base station with an overlapping radio footprint that extendsinto the DAS, such as the external base station 112. Any remote unitthat detects an external downlink signal can provide the externaldownlink signal to the measurement subsystem 118. The measurementsubsystem 118 can measure the external downlink signal by extractingsystem information parameters from the external downlink signal. Systeminformation parameters can include cell IDs and pilot power (e.g., theReference Signal Received Power in an LTE signal) of the externaldownlink transmission. The measurement subsystem can provide the systeminformation parameters to the OAM-SON unit 120.

The OAM-SON unit 120 can use the measurements provided by themeasurement subsystem to determine a mapping of the external celldetected by the remote units 126 a-c. For example, the OAM-SON unit 120can include a general purpose processor that determines if any of themeasured external cell IDs have a pilot power greater than apre-determined threshold. If a measured external cell ID does have apilot power greater than a pre-determined threshold, then the OAM-SONunit 120 can store an indication of the measured downlink signal pilotpower in a software-implemented database. The OAM-SON unit can storeindications of all external cell pilot powers that were detected byremote units 126 a-c in a two-dimensional software array in anon-volatile memory or random access memory. The two-dimensionalsoftware array can be visualized as a table.

FIG. 4 shows a table that maps the external cell pilot powers detectedby each remote unit from FIG. 2. Remote unit 202 e can detect thedownlink radio signals of external cell 206 a. If the detected downlinkradio signal is greater than a predetermined threshold, then the OAM-SONunit can indicate the external pilot power that was detected by remoteunit 202 e in the two-dimensional software array shown In FIG. 4. TheOAM-SON unit maps the detected external pilot powers that fall above apredetermined threshold for each remote unit that detects the externaldownlink signals. The mapping of external cells to remote units can bereferred to as an External Cell Mapping Table.

The DAS OAM-SON unit 120 can report the External Cell Mapping Table tothe DAS element management system 102. The External Cell Mapping Tablecan be used to restrict possible internal cell ID selection. Forexample, the DAS element management system 102 and the operator networkmanagement system 104 can refer to the External Cell Mapping Table whenselecting internal cell IDs in order to avoid collisions with thedetected external cell IDs.

In block 304 of FIG. 3, OAM-SON unit 120 and the measurement subsystem118 can determine a mapping of internal cells from measurements ofinternal downlink signals. Internal downlink signals can includedownlink signals from base stations communicatively coupled to thedistributed antenna system (e.g., internal base stations 106 a-b). Theinternal base stations 106 a-b can provide the internal downlink signalsto head-end unit 116. The measurement subsystem 118 can measure theinternal downlink signals provided to the head-end unit 116 and extractthe system information parameters from the internal downlink signals.Similar to the external downlink signals, internal downlink signals caninclude an identification of the pilot power and the cell ID. Themeasurement subsystem 118 can provide the measured system informationparameters to the OAM-SON unit 120, which can use the system informationparameters to determine a mapping of the internal cells. For example,the OAM-SON unit 120 can include a general purpose processor and amemory, discussed above with respect to block 304. If the measured pilotpower of the internal signal is greater than a pre-determined threshold,the OAM-SON unit 120 can store an indication of the measured downlinksignal pilot power in a software-implemented database in atwo-dimensional software array in the memory. The two-dimensionalsoftware array mapping internal cells to remote units can be visualizedas a table.

FIG. 5 shows a table that maps the internal cell pilot powers associatedwith the remote units from FIG. 2. For example, remote units 202 a-b,202 e are associated with internal cell 204 a. Remote units 202 c-d areassociated with internal cell 204 b. And remote unit 202 p is associatedwith internal cell 204 d. For each of the remote units 202 a-p in theDAS, the OAM-SON unit can indicate the pilot power of the downlinksignal from the associated internal cell. The mapping of internal cellsassociated with remote units can be referred to as an Internal CellMapping Table.

In block 306 of FIG. 3, the measurement subsystem 118 and the OAM-SONunit 120 can determine relation information of neighboring cells foreach remote unit in the DAS. Neighboring cells can include any cellswith radio footprints that overlap with the coverage zone for a givenremote unit. To determine the mapping, the OAM-SON unit 120 can setremote units with a given cell ID to detect over-the-air signalsradiated by neighboring remote units. For example, for each internalcell ID, the OAM-SON unit 120 can set remote units associated with theinternal cell ID to a radio-monitoring mode while remote units mapped todifferent internal cell IDs radiate downlink signals. In the exampleshown in FIG. 2, remote units 202 a-b, 202 e-f, associated with internalcell 204 a, can be set to a radio monitoring mode while remote units 202c-d, 202 g-h, and 202 i-p are set to radiate signals. For each of theremote units 202 a-b, 202 e-f set to a radio monitoring mode,measurement subsystem 118 can measure the over-the-air signals providedfrom the radiating remote units 202 c-d, 202 g-h, and 202 i-p anddetermine if the over-the-air signals have a pilot power greater than apre-determined threshold. For any detected over-the-air signals thathave a pilot power greater than a pre-determined threshold, theradiating signal can come from a neighboring cell. For example, forremote units 202 e-f, remote units 202 i-j can provide over-the-airsignals from neighboring cell #3 204 c. The measurement subsystem 118can provide the measured pilot powers of signals above thepre-determined threshold to the OAM-SON unit 120.

For each remote unit 202 a-p, the OAM-SON unit 120 can store anindication of the pilot power levels from any neighboring cells in a twodimensional software array in memory. As the External Cell Relationtable indicates which external cells 206 a-d are neighboring cellsdetected by a given remote unit, the OAM-SON unit 120 can store anindication of the pilot power levels of both neighboring internal cells204 a-d and neighboring external cells 206 a-c in the software array.FIG. 6 shows a table that indicates neighboring cells (both internal andexternal) for each remote unit from FIG. 2. The relation information ofneighboring cells to remote units can be referred to as a neighboringcell relation table. While FIG. 6 only depicts whether the neighboringcells are internal or external, the neighboring cell relation table canalso indicate the measured pilot power levels of the neighboringexternal cells and internal cells. For example, the OAM-SON unit 120 canstore, in the neighboring cell relation table, the measurements of pilotpower levels provided from internal cells and external cells as detectedby each remote unit in the DAS. The neighboring cell relation table canalso include measured parameters related to the detected cells,including Mobile Network Code, Mobile Country Code, technology, channelbandwidth, and frequency.

In some aspects, the operator network management system 104 can updatethe neighboring cell relation table. By updating the indication ofneighboring external and internal cells, hand-in and hand-out proceduresfor user devices can be smoothly supported by minimizing lostconnections during hand-over. For example, the operator networkmanagement system 104 can update the neighboring cell relation table inresponse to changes to the network environment (e.g., with changes tothe number of external cells 206 a-c detected by remote units 202 a-p).

In block 308, the DAS element management system 102 or the operatornetwork management system 104 can configure the DAS and internal basestations based on the information in the External Cell Mapping Table,Internal Cell Mapping Table, and neighboring cell relation table. Forexample, the operator network management system 104 can configure theDAS and the internal base stations by reconfiguring the selection ofinternal cell IDs 204 a-d assigned to base stations of internal cells204 a-d to avoid conflicting with the external cell IDs 206 a-c. In someaspects, the operator network management system 104 can also configurethe external base stations associated with external cells 206 a-c basedon the information in the External Cell Mapping Table, Internal CellMapping Table, and neighboring cell relation table. The RAN elementmanagement system 100 can send instructions to adjust the cell ID tointernal base stations associated with internal cell IDs 204 a-c orexternal base stations associated with external cells 206 a-c,accordingly.

In another aspect, the operator network management system 104 canconfigure the DAS by using the Internal Cell Mapping Table, ExternalCell Mapping Table, and neighboring cell relation table to determine oneor more gating cells associated with remote units located in proximityof pre-determined handover areas to and from external cells. Examples ofhandover areas include entry points and exit points of a building. Agating cell can include a cell that has a coverage area that overlapswith a neighboring cell. A coverage area for a cell can include theaggregate coverage areas of all remote units within the cell. Forexample, internal cell 204 c has a total coverage area serviced byremote units 202 i-j and 202 m-n. User devices in motion and moving fromthe coverage area of one cell to another cell can use a gating cell toseamlessly transition from the first cell to the second cell withoutdropping on-going communication.

To determine gating cells, the DAS element management system 102 canprovide the neighboring cell relation table to the operator networkmanagement system 104. The operator network management system 104 canuse the information in the neighboring cell relation table to determinewhich remote units are associated with an internal cell ID and anexternal cell ID, such that the remote unit is located in an overlappingarea of the radio footprints between the external cell and internalcell. For example, remote units 202 i, 202 m in FIG. 2 can be associatedwith internal cell 204 c as well as external cell 206 a. The operatornetwork management system 104 can identify internal cell 204 c andexternal cell 206 a as gating cells for user devices that are within thecoverage areas of remote units 202 i, 202 m and optimize the internalcell 204 c (e.g., internal base station 106) and external cell 206 a(e.g., external base station 112) for handover requests when userdevices are moving to and from internal cell 204 c and external cell 206a. For example, when user devices are moving from external cell 206 a tointernal cell 204 c, the operator network management system 104 caninstruct internal cell 204 c (e.g., internal base station 106) toinitiate handover procedures as defined by the carrier technology. Theoperator network management system 104 can synchronize internal cell 204c and the external cell 206 a with the packet data being communicatedwith the user device. Similarly, when a user device is moving frominternal cell 204 c to external cell 206 a, the operator networkmanagement system 104 can instruct external cell 206 a to initiatehandover procedures for the user device.

The internal cell relation table, external cell relation table, andneighboring cell relation table can be created at the commissioning ofthe DAS and can also be updated on a regular schedule in order to updatethe DAS configuration in response to a change in the radio environment.For example, when a new neighboring external base station is installedin the RAN, the DAS can automatically and efficiently detect theexternal base station and the corresponding external cell ID using theaspects discussed herein. The operator network management system 104 caninclude the new external cell ID in the internal cell relation table,external cell relation table, and neighboring cell relation table andre-configure the DAS based on the updated information.

Generating a Radio Environment Map That Indicates the Relative Positionsof User Devices

In certain aspects, the pilot power levels indicated in the neighboringcell relation table can be compared with additional pilot powermeasurements detected by each user device within the coverages area ofthe DAS. The comparison can be used to generate a radio environment thatincludes the relative positions of the user devices. For example, FIG. 8shows an example of three user devices 808 a-c positioned in differentgeographic locations within a DAS 800. The DAS 800 includes five remoteunits 802 a-e communicating with a single internal cell. External cells806 a-b have radio footprints that extend into the DAS 800.Specifically, external cell 806 a has a radio footprint that extendsinto the coverage zones of remote units 802 a, 802 c, and external cell806 b has a radio footprint that extends into the coverage zones ofremote units 802 b, 802 d. The depicted signal fronts of each externalcell 806 a-b and the remote units 802 a-e are related to a minimum powerlevel threshold that can be detected by the DAS measurement subsystem.

Each user device 808 a-c can be located at different positions in theDAS 800 at different times. As depicted in FIG. 8, user devices 808 a-bare located at the cell-edge of the internal cell and user device 808 cis located at the cell-center of the internal cell. To determine thepositions of the user devices 808 a-c relative to the remote units 802a-e, the RAN element management system 100 or one of the OAM-SON units108 a-b of the internal base stations 106 a-b can compare cell powermeasurements of downlink signals (e.g., pilot power levels) detected byeach user device 808 a-c with the pilot power levels detected by eachremote unit 802 a-e as indicated in the neighboring cell relation table.

For example, the RAN element management system 100 or one of the OAM-SONunits 108 a-b of internal base stations 106 a-b can collect powermeasurements of downlink signals detected by each user device 808 a-c.Additionally, as indicated above, pilot power levels measured at theremote units 802 a-e can be stored by the DAS OAM-SON unit 120 in aneighboring cell relation table. A common interface between thecomponents of the DAS 800 and the components of the associated RAN canbe used to provide the pilot power levels indicated in the neighboringcell relation table from the DAS 800 to the RAN (e.g., the OAM-SON units108 a-b of internal base stations 106 a-b or to the RAN elementmanagement system 100). For example, a common interface between the DAS800 and the RAN can be used to communicate measurements taken by themeasurement subsystems 118, 708 (e.g., the neighboring cell relationtable, downlink power levels at the remote units 126, etc.) to the RAN.

Via radio communications protocols, the operator network managementsystem 104, RAN element management system 100, or the internal basestations 106 a-b can use the collected power measurements to determinethe location of each user device 808 a-c relative to the remote units802 a-e. This information can be used to generate a radio coverage mapthat identifies the locations of user devices 808 a-c, which in turn canbe used to determine dense areas of wireless traffic in the DAS 800.FIGS. 9-10 depict alternative architectures of a RAN and DAS thatinclude a common interface for communicatively coupling the operationsand management subsystems of the DAS and the internal base stations. Thecommon interface allows the DAS OAM-SON unit 120 to provide powermeasurements taken by the measurement subsystems 118, 708 to the OAM-SONunits 108 a-b of the internal base stations 106 a-b or the RAN elementmanagement system 100. While the use of a common interface to couple theRAN and DAS 800 is described with respect to FIG. 8, these alternativearchitectures including a common interface between the RAN and DAS 800can be applied to all features described herein.

For example, FIG. 9 depicts a RAN and DAS management architecturesimilar to the architecture shown in FIG. 1 but with a common interface902 communicatively coupled to a DAS element management system 102 and aRAN element management system 100. The RAN and DAS managementarchitecture can include an operator network management system 104communicatively coupled to the DAS element management system 102 and theRAN element management system 100. The architecture can also include aDAS head-end unit 116 communicatively coupled to remote units 126 a-cand to internal base stations 106 a-b. The RAN element management system100 can be communicatively coupled to the internal base stations 106 a-bas well as external base stations such as external base station 112. Asin FIG. 1, the head-end unit 116 can include an OAM-SON unit 120, aswitch 124, and a measurement subsystem 118. Each internal base station106 a-b can also include an OAM-SON unit 108 a and 108 b, and externalbase station 112 can include OAM-SON unit 114. Each of the components ofthe RAN and DAS management architecture function in a similar manner tothe corresponding components discussed with respect to FIG. 1.

The common interface 902 can include any interface for communicativelycoupling the DAS element management system 102 and the RAN elementmanagement system 100. For example, the common interface 902 can includean Ethernet interface or a serial interface such as RS-232. The commoninterface 902 can provide a communication path so that the DAS cantransfer measurement parameters to the RAN.

While FIG. 9 depicts the common interface 902 as coupled to the DASelement management system 102 and the RAN element management system 100,the other components of the RAN and DAS can also be connected. Forexample, FIG. 10 depicts a management architecture similar to thearchitecture shown in FIGS. 1 and 9. Similar to FIGS. 1 and 9, antennaports of the internal base stations 106 a-b and antenna ports of the DAShead-end unit 116 can be communicatively coupled with an RF interface(e.g., using coaxial cables). In addition, the OAM-SON units 108 a-b ofinternal base stations 106 a-b, respectively, can be communicativelycoupled to the OAM-SON unit 120 of head-end unit 116 using a commoninterface 1002. The RAN and DAS management architecture in FIG. 10 caninclude an operator network management system 104 communicativelycoupled to a DAS element management system 102 and a RAN elementmanagement system 100. The architecture can also include a DAS head-endunit 116 communicatively coupled to remote units 126 a-c and to internalbase stations 106 a-b. The RAN element management system 100 can becommunicatively coupled to the internal base stations 106 a-b as well asexternal base stations such as external base station 112. As in FIGS. 1and 9, the head-end unit 116 can include an OAM-SON unit 120, a switch124, and a measurement subsystem 118. Each internal base station 106 a-bcan also include an OAM-SON unit 108 a and 108 b, and external basestation 112 can include OAM-SON unit 114. Each of the components of theRAN and DAS management architecture 100, 102, 104, 106 a-b, 108 a-b,112, 114, 116, 118, 120, 124, 126 a-c function in a similar manner tothe corresponding components discussed with respect to FIG. 1.

The interface between the RAN and the DAS, such as the common interface902 or the common interface 1002, can be used to provide power levelmeasurements collected by the measurement subsystem 118 (e.g., downlinksignal pilot power levels of remote units as indicated in theneighboring cell relation table) from the DAS to the RAN. The OAM-SONunits 108 a-b of the internal base stations 106 a-b or the RAN elementmanagement system 100 can determine a radio coverage map by comparingthe collected user device power level measurements with power levelmeasurements indicated in the neighboring cell relation table determinedby the OAM-SON unit 120. FIG. 11 is a flowchart describing a process fordetermining a radio coverage map and determining the relative positionsof the user devices.

In block 1102, OAM-SON units 108 a-b or the RAN element managementsystem 100 collect power levels of downlink signals detected at userdevices. For example, user devices can routinely determine pilot powerlevels of the downlink signals and provide the pilot power levels tocomponents of the RAN, as part of standard signaling protocols. Forexample, according to Radio Resource Control signaling protocols, userdevices can provide power level measurements of downlink pilot signalsto components of the RAN as part of a cell measurement report procedure.The OAM-SON units 108 a-b or the RAN element management system 100 cancompile the measurements collected from the RAN in a two-dimensionaldata structure mapping the pilot power level detected at each userdevice at each cell. For example, FIG. 12 is a table mapping the pilotpower levels detected by each user device shown in FIG. 8 for each cellin FIG. 8. User device 808 a detected and measured a pilot power levelof −90 decibels from the internal cell. User devices 808 b-c detectedand measured pilot power levels of −90 decibels and −85 decibels,respectively, from the internal cell. Each of the user devices 808 a-calso detected and measured pilot power levels provided by external cells806 a-b. For example, pilot signals provided from external cell 806 awere measured at −95 decibels at user device 808 a, −125 decibels atuser device 808 b, and −125 decibels at user device 808 c. Pilot signalsprovided from external cell 806 b were measured with power levels at 125decibels at user device 808 a, 95 decibels at user device 808 b, and−125 decibels at user device 808 c.

Additionally, downlink pilot power measurements measured at the remoteunits 802 a-c (e.g., downlink power measurements indicated in aneighboring cell relation table) can be provided from the DAS to the RANvia a common interface 902. For example, the power levels of the pilotsignals detected at the remote units in the DAS can be provided from theneighboring cell relation table discussed above with respect to FIG. 6.For example, the OAM-SON unit 120 in the head-end unit 116 can generatethe neighboring cell relation table, which indicates the pilot powerlevels of each internal and external detected by each remote unit in theDAS. The OAM-SON unit 120 can provide the neighboring cell relationtable to the RAN element management system 100 via the common interface902. Alternatively, the OAM-SON unit 120 can provide the neighboringcell relation table to the OAM-SON units 108 a-b of the internal basestations 106 a-b via the common interface 1002.

FIG. 13 shows a neighboring cell relation table for remote units 802 a-eshown in FIG. 8. Pilot signals provided from external cell 806 detectedby remote unit 802 a are measured at −110 decibels. Pilots signalsprovided from external cell 806 a detected by remote units 802 b, 802 c,802 d, and 802 e are measured at −125 decibels, −100 decibels, −125decibels, and −125 decibels, respectively. Pilot signals from externalcell 806 b are measured and indicated for each remote unit 802 a-e.

In block 1104, the RAN element management system 100 or the OAM-SONunits 108 a-b of internal base stations 106 a-b can compare power levelsof the pilot signals detected at the user devices with power levels ofpilot signals detected at remote units. For example, the RAN elementmanagement system 100 or the OAM-SON units 108 a-b can compare the powerlevels detected at the user devices and the power levels detected at theremote units by taking a difference of the power levels. FIG. 14 shows atable mapping the difference in pilot power levels detected by remoteunits 802 a-e and by user devices 808 a-c. For example, external cell806 a provides a pilot signal that is measured by the remote unit 802 aand by the user device 808 a. The difference between the pilot powermeasured at remote unit 802 a and the pilot power measured at userdevice 808 a is (−95)-(−110) decibel-milliwatts (dBm). External cell 806b provides a pilot signal that is measured by the remote unit 802 a andthe user device 808 a. The difference between the measured power levelsof the pilot signal from external cell 806 b as detected by remote unit802 a and user device 808 a is (−125)-(−125) decibels. FIG. 14 shows asimilar comparison of pilot power levels provided from external cells806 a-b as detected by each remote unit 802 a-e and by each user device808 a-c.

In block 1106, the RAN element management system 100 or the OAM-SONunits 108 a-b can determine the location of the user devices 808 a-crelative to the remote units 802 a-e by using the comparisons of thepilot signal power levels. Positions of the user devices 808 a-c can bedetermined using a maximum likelihood criterion. For example, if pilotthe power level from a neighboring external cell measured at a remoteunit and the pilot power level from the same neighboring external cellmeasured at the user device are similar, then the comparison canindicate that the user device is close in proximity to the remote unitand at the cell-edge of the external cell. If the pilot power levelmeasured at a remote unit and a user device are different, then thecomparison can indicate that the user device is located away from theremote unit. Comparing the differences in measured power levels acrosseach user device can allow the DAS element management system 102 or theRAN element management system 100 to determine a radio coverage map ofthe user devices, estimating the position of each user device relativeto each remote unit.

For example, returning to FIG. 14, comparing the differences in powerlevels across each user device 808 a-c shows which user devices 808 a-care closer to each of the remote units 802 a-e. Table cell 1402, whichlists the lowest differences in power levels for user device 808 a,indicates that user device 808 a is closest in proximity to remote unit802 c. Table cell 1404 indicates that user device 808 b is closest inproximity to remote unit 802 d. Table cell 1406 indicates that userdevice 808 c is closest in proximity to remote unit 802 e.

Power and Carrier Frequency Allocations to Outer Remote Units

In some aspects, external cells 206 a-c can cause signal interference toremote units that fall within the coverage zones of both external cells206 a-c and internal cells 204 a-d due to conflicting frequency bands.For example, remote units 202 e, 202 i, 202 m located at the edges ofthe DAS can receive interfering signals of conflicting frequency bandsfrom external cell 206 a. Similarly, remote units 202 o, 202 p, 202Llocated at the edges of the DAS can receive interfering signals ofconflicting frequency bands from external cell 206 c. Based on signalinterference from external cells 206 a-c, the DAS OAM-SON unit 120 canmodify the selection of carrier frequencies allocated to remote units onthe edges of internal cells (outer remote units). For example, outerremote units can be located close to the windows of a building and thussusceptible to interference from signals from external cells 206 a-cleaking into the building. Outer remote units can detect interferencefrom external cells by measuring pilot powers of specific external cells206 a-c for a given carrier frequency. Power measurements above apre-defined threshold can indicate high signal interference from theexternal cell for the measured carrier frequency.

As an example, remote unit 202 m, which can be an outer remote unit, canbe affected with high signal interference due to signals from externalcell 206 a. A measurement subsystem within the remote unit 202 m candetermine the signal-to-interference ratio of incoming downlink signalsfrom internal cell 204 c and provide the signal-to-interference ratio tothe head-end unit 116. In another aspect, the measurement subsystem 118within head-end unit 116 can measure the signal-to-interference ratio ofdownlink signals from internal cell 204 c. A low signal-to-interferenceratio can indicate conflicting signals on the same carrier frequencyfrom external cell 206 a. In response, the DAS OAM-SON unit 120 canallocate fewer carrier signals to remote units affected by high externalcell signal interference. Carrier signals allocated to remote unitsaffected by high signal interference can be reduced by, for example,allocating a fewer number of internal cells 204 a-c to the affectedremote units. For a given composite power available at the remote unit,fewer carriers per remote unit can result in higher power per carrierfrequency. By reducing the number of carriers allocated to remote unit202 m (the remote unit affected by high external cell interference),remote unit 202 m can have better power dominance over any externalinterference due to signals from external cell 206 a.

By reducing the number of carriers allocated per selected remote units,total power per channel can be increased as total available transmitpower is used on fewer channels. Reducing the number of carriersallocated to outer remote units in a building can help keep indoor celldominance over the interference from external cells 206 a-c leaking intothe building.

Additionally, the DAS OAM-SON unit 120 can optimize the DAS by avoidingallocating the same carrier frequencies as used by external cells 206a-c on specific remote units affected by interference by that frequency.For example, if remote unit 202 m detects high signal interference dueto signals from external cell 206 a on carrier frequency X, OAM-SON unit120 can avoid allocating carrier frequency X to remote unit 202 m. Ifexternal cell 206 a is emitting interfering signals from two carrierfrequencies X and Y, then OAM-SON unit 120 can allocate one interferingcarrier frequency X or Y to remote unit 202 m. By omitting one of theinterfering carrier frequencies, the total available power on theallocated carrier frequency will be higher due to reduced power sharingwith the omitted carrier. In some aspects, an outer remote unit candetect very large signal interference (e.g., above a pre-determinedthreshold) from external cells 206 a-c. In response, the OAM-SON unit120 can allocate a carrier frequency to the affected outer remote unitsthat is different from the interfering carrier frequency. Thus, in casesof very large signal interference from external cells 206 a-c, outerremote units within the DAS can be allocated carrier frequencies notused by external cells 206 a-c.

The decision on the number of carrier frequencies to be allocated onspecific remote units can be driven by interference power thresholds,which the DAS OAM-SON unit 120 can define for each frequency. If a firstinterference power threshold is exceeded by signal interference fromexternal cells 206 a-c, then the OAM-SON unit 120 can avoid allocatingone of the interfering carrier frequencies. If a higher secondinterference power threshold is exceeded by signal interference from anexternal cell 206 a-c, then the DAS OAM unit 120 can avoid allocatingmultiple interfering carrier frequencies as used by external cells 206a-c.

While the present subject matter has been described in detail withrespect to specific aspects and features thereof, it will be appreciatedthat those skilled in the art, upon attaining an understanding of theforegoing may readily produce alterations to, variations of, andequivalents to such aspects and features. Accordingly, it should beunderstood that the present disclosure has been presented for purposesof example rather than limitation, and does not preclude inclusion ofsuch modifications, variations or additions to the present subjectmatter as would be readily apparent to one of ordinary skill in the art.

What is claimed is:
 1. A method, comprising: determining a mapping ofexternal cells from measurements of external downlink signals receivedby a remote unit of a distributed antenna system, the remote unitproviding wireless communication within a coverage zone; determining amapping of internal cells from measurements of internal downlink signalsprovided by base stations communicatively coupled to a head-end unit ofthe distributed antenna system; determining relation information ofneighboring cells that include radio footprints that overlap with thecoverage zone of the remote unit; and configuring the distributedantenna system and the base stations based on the mapping of externalcells, the mapping of internal cells, and the relation information ofneighboring cells.
 2. The method of claim 1, wherein the measurements ofexternal downlink signals include external cell identifiers, a mobilecountry code, a mobile network code, a type of carrier technology, asignal bandwidth, a signal frequency, and power levels of downlink pilotsignals.
 3. The method of claim 2, wherein external cells include cellsassociated with additional base stations not communicatively coupled tothe distributed antenna system, wherein internal cells include cellsassociated with the base stations communicatively coupled to thehead-end unit, and wherein determining the mapping of external cellscomprises indicating, in an external cell mapping table, the powerlevels of downlink pilot signals if the power levels of downlink pilotsignals are greater than a pre-determined threshold.
 4. The method ofclaim 1, wherein configuring the distributed antenna system includesadjusting an allocation of internal cell identifiers to avoidconflicting with external cell identifiers indicated by the mapping ofthe external cell identifiers.
 5. The method of claim 1, whereinconfiguring the distributed antenna system includes determining a gatingcell associated with the remote unit, wherein the remote unit is locatedin an overlapping area within a first radio footprint and a second radiofootprint.
 6. The method of claim 1, further comprising revising themapping of external cells, the mapping of internal cells, and therelation information of neighboring cells in response to a change in aradio environment of the distributed antenna system.
 7. The method ofclaim 1, further comprising: collecting signal power measurements ofpilot signals, the signal power measurements performed by a user devicewithin the coverage zone; comparing the signal power measurements withneighboring cell signal power measurements indicated in the relationinformation of the neighboring cells; and determining a radioenvironment map estimating a position of the user device with respect tothe remote unit.
 8. A head-end unit, comprising: a measurement subsystemconfigured to measure external downlink signals detected by a remoteunit of a distributed antenna system and measure internal downlinksignals provided from an internal base station communicatively coupledto the distributed antenna system; and an operation and managementsystem configured to (i) determine, from the external downlink signals,a mapping of external cells detected by the remote unit, (ii) determine,from the internal downlink signals, a mapping of internal cells, and(iii) determine relation information of neighboring cells that includeradio footprints that overlap with a coverage zone of the remote unit,wherein the head-end unit is configured to provide wirelesscommunication from the internal base station to the remote unit of thedistributed antenna system.
 9. The head-end unit of claim 8, wherein themeasurement subsystem is configured to measure the external downlinksignals by determining external downlink signal power levels andexternal cell identifiers and wherein the measurement subsystem isconfigured to measure the internal downlink signals by determininginternal downlink signal power levels and internal cell identifiers. 10.The head-end unit of claim 9, wherein the operation and managementsystem is configured to determine the mapping of external cells byindicating, in an external cell mapping table, the external downlinksignal power levels if the external downlink signal power levels aregreater than a pre-determined threshold.
 11. The head-end unit of claim8, wherein the operation and management system is further configured toprovide the mapping of external cells, the mapping of internal cells,and the relation information of neighboring cells to an operator networkmanagement system, and wherein the operator network management system isconfigured to optimize the distributed antenna system by adjusting anallocation of internal cell identifiers to avoid conflicting withexternal cell identifiers indicated by the mapping of external cells.12. The head-end unit of claim 8, wherein the operation and managementsystem is further configured to provide the mapping of external cells,the mapping of internal cells, and the relation information ofneighboring cells to an element management system, and wherein theelement management system is configured to optimize the distributedantenna system by sending, to an operator network management system,instructions for adjusting an allocation of internal cell identifiers toavoid conflicting with external cell identifiers indicated by themapping of external cells.
 13. The head-end unit of claim 8, wherein theoperation and management system is further configured to provide themapping of external cells, the mapping of internal cells, and therelation information of neighboring cells to an element managementsystem, wherein the element management system is configured to optimizethe distributed antenna system by determining a gating cell associatedwith the remote unit, and wherein the remote unit is located in anoverlapping area within a first radio footprint and a second radiofootprint.
 14. The head-end unit of claim 8, wherein the operation andmanagement system is further configured to collect signal powermeasurements for pilot signals detected by user devices, compare thesignal power measurements with neighboring cell signal powermeasurements indicated in the mapping of the neighboring cells, anddetermine a radio environment map estimating positions of the userdevices within the distributed antenna system.
 15. A distributed antennasystem, comprising: one or more remote units configured to providewireless communication to user devices within a coverage zone; and ahead-end unit communicatively coupled to the one or more remote units,the head-end unit including an operation and management systemconfigured to determine a mapping of external cells, a mapping ofinternal cells, and relation information of neighboring cells for eachremote unit in the distributed antenna system and provide the mapping ofexternal cells, the mapping of internal cells, and the relationinformation of neighboring cells to an element management systemcommunicatively coupled to the head-end unit, wherein the elementmanagement system is configured to optimize the distributed antennasystem based on the mapping of external cells, the mapping of internalcells, and the relation information of neighboring cells.
 16. Thedistributed antenna system of claim 15, wherein the element managementsystem is configured to optimize the distributed antenna system bysending, to an operator network management system, instructions foradjusting an allocation of internal cell identifiers to avoidconflicting with external cell identifiers indicated by the mapping ofexternal cells.
 17. The distributed antenna system of claim 15, whereineach of the one or more remote units include a measurement subsystemconfigured to measure internal downlink signals and external downlinksignals and provide measurements of the internal downlink signals andmeasurements of the external downlink signals to the head-end unit. 18.The distributed antenna system of claim 17, wherein the measurements ofthe internal downlink signals include internal downlink signal powerlevels and internal cell identifiers and the wherein the measurements ofthe external downlink signals include external downlink signal powerlevels and external cell identifiers.
 19. The distributed antenna systemof claim 15, wherein the distributed antenna system is communicativelycoupled to a radio access network configured to collect downlink signalpower levels of pilot signals detected at the user devices within thecoverage zone, compare the downlink signal power levels with neighboringcell signal power measurements indicated in the relation information ofneighboring cells, and determine a radio environment map for estimatingpositions of the user devices within the distributed antenna system. 20.The distributed antenna system of claim 19, wherein the radioenvironment map indicates, for each of the one or more remote units,relative positions of the user devices.